fix (#1112)

.github/workflows/build-ubuntu-2004.yml

@@ -26,7 +26,7 @@ jobs:
     strategy:
       matrix:
         config: [release, debug]
-        os: [ubuntu-18.04]
+        os: [ubuntu-20.04]
     
     steps:
     - name: Checkout

README.md

@@ -65,7 +65,8 @@ Other resources to learn how to setup the build system:
   | Mac OS X (latest)              | :white_check_mark: | :white_check_mark: |
   | Ubuntu 14.04.x LTS             | :white_check_mark: |                    |
   | Ubuntu 16.04.x LTS             | :white_check_mark: |                    |
-  | Ubuntu 18.04.x LTS             | :white_check_mark: | :white_check_mark: |
+  | Ubuntu 18.04.x LTS             | :white_check_mark: |                    |
+  | Ubuntu 20.04.x LTS             | :white_check_mark: | :white_check_mark: |
   | Ubuntu (latest)                | :white_check_mark: | :white_check_mark: |
   | Windows 7.1                    | :white_check_mark: |                    |
   | Windows 8.1                    | :white_check_mark: |                    |